When thieves hijack a collection of stuffed animals from a country auction, Frank and Joe Hardy pursue the getaway car and are drawn into a thrilling mystery. At the same time, the young detectives’ father—famed private investigator Fenton Hardy—is tracking down an industrial spy ring. This suspense-filled story of pursuit and detection will keep the reader breathlessly following the chain of unexpected developments that lead Frank and Joe to the spine-tingling climax in the wilds of Northern Canada.

In a series of hair-raising adventures both on land and undersea the teenage brother detectives pit their wits against some of the most ruthless criminals they have ever encountered. It all starts when Frank and Joe are skin diving just for fun and the thrill of exploring the undersea world. Suddenly, deep in the waters that flow near the foot of Pirates’ Hill, a mysterious skin diver fires a spear through Frank’s air hose. From this moment on, danger is never far away. The very lives of the boys are at stake as they, along with the help of their pals, uncover a mystery involving an old Spanish cannon and a fabulous sunken treasure.

Triggered by the disappearance of a brilliant young professor, this mystery takes the Hardy boys first to Kenworthy College, where they find a puzzling message on an examination paper. But then, a new clue is unearthed that sends the young detectives to the Honeycomb Caves. After many dangerous encounters, Frank and Joe discover a powerful searchlight in one of the craggy caverns along the seacoast. In the brilliant white glare of the searchlight, the startling secret of the caves is dramatically revealed.

An invitation from Cap Bailey, science teacher at Bayport High, to accompany him out West to Wildcat Swamp on an archaeological expedition triggers off a series of dangerous events for Frank and Joe Hardy. On their way West the boys and Cap have a near-fatal accident in a private plane which has been sabotaged. Though warned to leave the area, Frank, Joe, and Cap doggedly remain until they have caught the cunning ex-convicts they are up against in this swift-paced adventure.

During Mr. Hardy’s investigation of a ruthless gang of terrorists, Frank and Joe witness an explosion in the sky near an airborne dirigible owned by Quinn Air Fleet. The young detectives look into a clue that takes them into a new animal park outside Bayport, where they are lured into a trap by an unknown enemy. Problems arise for the park owner as he receives pressure from a competitor and a real-estate firm to sell out. Strange occurrences at the park also frighten the visitors and animals. Frank and Joe take up the case despite fore warnings.

With two cases in tow, the Hardy boys look to Turner mill for clues. Determined to learn the secret of the old mill, Frank and Joe employ a clever ruse to gain entrance, only to find themselves trapped. How the young detectives extricate themselves from this dangerous situation and unravel mysteries will keep readers tense with suspense!

When an ancient stone idol disappears, the Hardy Boys are off on another fast-paced adventure. It's a mystery that takes the boys from a primitive village in the Andes Mountains to Antarctica and finally to Easter Island. By using their fine investigative skills, the Hardy Boys find that the mystery of the stone idol is not what it seems!

Rarely do magicians reveal their professional secrets. Consequently Frank and Joe Hardy are amazed when a well-known magician, the Incredible Hexton, offers to reveal the secret of his “Vanishing Man Act” and invited Mr. Hardy to be the subject. When their detective father fails to reappear, his sons are convinced that something sinister is afoot, despite Hexton’s insistence that Mr. Hardy is playing a joke on them. While desperately searching for their father, Frank and Joe find themselves working with SKOOL, a U.S. organization of secret agents pitted against UGLI, an international ring of spies stealing government secrets domestically and internationally. The young detective’s gripping adventures culminate in a dramatic climax when they unmask the secret agent on Flight 101.

Difficult assignments are nothing new to the Hardy boys and this one that takes them to the Deep South is particularly challenging. Their mission: to vindicate a long-dead Confederate general, disgraced during the Civil War because he was accused of stealing hidden gold belonging to a bank. Skillfully avoiding booby traps and flying bullets, the boys persevere in their perilous quest. The arduous search is full of surprises that will thrill all fans of the Hardy boys.